Tread surface of a footwear outsole



FIG. 1 is a bottom, side perspective view of a tread surface of a footwear outsole; and,

FIG. 2 is a bottom view of the tread surface of a footwear outsole of FIG. 1.

The ornamental design that is claimed is shown in solid lines and by surface shading on claimed surfaces in the drawings. The broken (dashed) lines shown in FIGS. 1 through 2 are included for the purpose of illustrating environmental elements only and form no part of the claimed design. 

I claim the ornamental design for a tread surface of a footwear outsole, as shown and described. 